Modern automotive engines include electronic engine controls which vary operating parameters of the engine, such as air-fuel ratios and ignition timing, to achieve optimum performance. Such control systems are capable of changing engine operating parameters in response to a variety of external conditions.
Engines designed to operate efficiently with different fuels, or a mixture of different fuels, utilize electronic engine control systems to change the engine operating parameters in response to the type of fuel being delivered to the engine. Such systems utilize a sensor to detect the type of fuel being delivered to the engine and an electronic engine control to vary the operating parameters accordingly. One such system is disclosed in U.S. Pat. No. 4,706,629 issued to Wineland et al.
The time required for the sensor to transmit the fuel-type indication, and the time required by the electronic engine control to change the engine operating parameters in response to that indication, are invariably shorter than the time required for the fuel itself to travel from the sensor to the engine. If the sensor is located away from the engine, for instance near the fuel tank, the engine operating parameters will be changed by the engine control system for the new fuel-type before the new fuel has arrived at the engine. This can result in poor performance and combustion efficiency until the conforming fuel reaches the engine. This problem is particularly acute when the fuel in the tank stratifies. Stratification can occur, for instance, in cold weather when the tank contains a mixture of gasoline and methanol. Under these conditions, the fuel pump will pick up different layers of the fuel at different times, the sensor will detect the change in the fuel, and the engine operating parameters will be changed before the detected fuel reaches the engine. As a result, the engine will suffer a temporary loss of performance and efficiency because of the disparity between the engine operating parameters and the fuel being utilized.